| 摘要 |
PROBLEM TO BE SOLVED: To provide wheels capable of easily passing steps difficult for wheels with small diameter to pass, while keeping the wheels compact. SOLUTION: A disc 2 having a projection of which tip outer peripheral diameter is set larger than the outer periphery of the wheels 1a, 1b is rotatably provided in an axle 4 of the wheels 1a, 1b such that the tip of the projection is positioned toward the advancing direction. The radius R of the disc 2 having the projection in the upper side from a line connecting a projection upper part C of the disc 2 having the projection with the center D of the axle 4 is set equal to the radius R of the wheels 1a, 1b. The projection is kept in the steady position by a weight 6. When the wheels 1a, 1b are rotated and reach a step, the projection contacts with the step ahead of the wheels 1a, 1b, and the wheels 1a, 1b are pushed up by the projection serving as an axis. As a result, the wheels 1a, 1b can easily pass the step, and the disc 2 having the projection is returned to the original position. COPYRIGHT: (C)2006,JPO&NCIPI
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